The broad objective of this proposal is to examine the mechanisms by which gastrointestinal hormones and neurotransmitters control the electrical and mechanical activity of smooth muscle of the antrum of human, cat and dog. The major emphasis in this study will be on human antral smooth muscle. The areas of particular interest are: a) the ionic basis and mechanism of production of the spontaneous electrical potential, b) the nature of the intramural nervous system and its influence on the spontaneous potential, and c) the site and mechanism of action of secretin, gastrin, pentagastrin, norepinephrine and isoprenaline. The general method of approach will be the measurement of electrical activity of single, smooth muscle cells and of bundles of antral smooth muscle cells in vitro with intracellular and sucrose gap techniques.